1 2 /** 3 * Copyright (C) 2018-present MongoDB, Inc. 4 * 5 * This program is free software: you can redistribute it and/or modify 6 * it under the terms of the Server Side Public License, version 1, 7 * as published by MongoDB, Inc. 8 * 9 * This program is distributed in the hope that it will be useful, 10 * but WITHOUT ANY WARRANTY; without even the implied warranty of 11 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the 12 * Server Side Public License for more details. 13 * 14 * You should have received a copy of the Server Side Public License 15 * along with this program. If not, see 16 * <http://www.mongodb.com/licensing/server-side-public-license>. 17 * 18 * As a special exception, the copyright holders give permission to link the 19 * code of portions of this program with the OpenSSL library under certain 20 * conditions as described in each individual source file and distribute 21 * linked combinations including the program with the OpenSSL library. You 22 * must comply with the Server Side Public License in all respects for 23 * all of the code used other than as permitted herein. If you modify file(s) 24 * with this exception, you may extend this exception to your version of the 25 * file(s), but you are not obligated to do so. If you do not wish to do so, 26 * delete this exception statement from your version. If you delete this 27 * exception statement from all source files in the program, then also delete 28 * it in the license file. 29 */ 30 31 #pragma once 32 33 #include <memory> 34 #include <string> 35 36 #include "mongo/base/disallow_copying.h" 37 #include "mongo/base/status.h" 38 39 namespace mongo { 40 41 constexpr StringData kLockFileBasename = "mongod.lock"_sd; 42 43 class StorageEngineLockFile { 44 MONGO_DISALLOW_COPYING(StorageEngineLockFile); 45 46 public: 47 /** 48 * Checks existing lock file, if present, to see if it contains data from a previous 49 * unclean shutdown. A clean shutdown should have produced a zero length lock file. 50 * Uses open() to read existing lock file or create new file. 51 * Uses boost::filesystem to check lock file so may throw boost::exception. 52 */ 53 StorageEngineLockFile(const std::string& dbpath, StringData fileName = kLockFileBasename); 54 55 virtual ~StorageEngineLockFile(); 56 57 /** 58 * Returns the path to the lock file. 59 */ 60 std::string getFilespec() const; 61 62 /** 63 * Returns true if lock file was not zeroed out due to previous unclean shutdown. 64 * This state is evaluated at object initialization to allow storage engine 65 * to make decisions on recovery based on this information after open() has been called. 66 */ 67 bool createdByUncleanShutdown() const; 68 69 /** 70 * Opens and locks 'mongod.lock' in 'dbpath' directory. 71 */ 72 Status open(); 73 74 /** 75 * Closes lock file handles. 76 */ 77 void close(); 78 79 /** 80 * Writes current process ID to file. 81 * Fails if lock file has not been opened. 82 */ 83 Status writePid(); 84 85 /** 86 * Truncates file contents and releases file locks. 87 */ 88 void clearPidAndUnlock(); 89 90 private: 91 std::string _dbpath; 92 std::string _filespec; 93 bool _uncleanShutdown; 94 95 class LockFileHandle; 96 std::unique_ptr<LockFileHandle> _lockFileHandle; 97 }; 98 99 } // namespace mongo 100